Typically, a valve controls a flowing direction of fluid, such as liquid and gas, a flow rate, or a similar condition. For example, the valve disclosed in JP2001-082526A is embodied as the piston valve for a damper. The valve is held to the rod, which comes in/out the tubular cylinder, so as to be movably inserted into the cylinder in the axial direction.
The piston valve includes the piston and the annular-plate shaped leaf valves. The piston is the valve disc formed in the cylinder to partition the expansion-side chamber and the compression-side chamber filled with hydraulic oil. The leaf valves are laminated on both sides in the axial direction of the piston. Furthermore, the piston includes the annular bosses, the seats, the openings, the expansion-side passage, and the compression-side passage. The bosses are formed on both sides in the axial direction of the piston to support the leaf valves. The seats are formed at outer peripheral sides of these respective bosses. The leaf valves are left from/seated on the seats. The openings are surrounded by the respective seats. The expansion-side passage allows the opening on the expansion-side chamber side to communicate with the compression-side chamber side. The compression-side passage allows the opening on the compression-side chamber side to communicate with the expansion-side chamber side.
During expansion of the damper, when the expansion-side chamber is pressurized and the pressure in the expansion-side chamber reaches the open-valve pressure of the leaf valve on the compression-side chamber side, the outer peripheral portion of the leaf valve is away from the seat on the compression-side chamber side, allowing a communication of the expansion-side passage. Therefore, the damper generates an expansion-side damping force caused by a resistance when the hydraulic oil passes through the expansion-side passage and moves from the expansion-side chamber to the compression-side chamber. On the contrary, during compression of the damper, when the compression-side chamber is pressurized and the pressure in the compression-side chamber reaches the open-valve pressure of the leaf valve on the expansion-side chamber side, the outer peripheral portion of the leaf valve is away from the seat on the expansion-side chamber side, allowing a communication of the compression-side passage. Therefore, the damper generates a compression-side damping force caused by a resistance when the hydraulic oil passes through the compression-side passage and moves from the compression-side chamber to the expansion-side chamber.
The piston disclosed in JP2001-082526A is a mold piston integrated with the piston ring made of synthetic resin, which is mounted to the outer periphery of the piston. Slidable contact with the inner peripheral surface of the cylinder via the piston ring allows the piston to smoothly move inside the cylinder.
To form such mold piston, the pistons that mount the annular-plate shaped base materials, which become the piston rings later, on the outer periphery are vertically stacked. The pistons are sequentially pushed into the heated mold to form the piston rings and to integrate the piston rings and the pistons. At this time, the pistons are pushed into the mold at a large force.
However, depending on the shape of the piston, when the pistons are vertically stacked coaxially and are pushed into the mold, the bosses of the overlapping pistons may not in contact with one another. For example, if the pistons are in contact with only parts at which the seat on the expansion-side chamber side meet the seat on the compression-side chamber side, contacted areas of the pistons may be extremely small.
Thus, with the extremely small contacted areas of the pistons, if the overlapping pistons are pushed into the mold, a load concentrates, possibly resulting in a deformation of the contact parts of the pistons. The deformation of the seats of the pistons provides gaps with the leaf valves left from/seated on the seats, possibly resulting in a leakage of hydraulic oil from the gaps. In the case where the piston, which is the valve disc, is used for the damper as described above, there may be a case that a desired damping force is not obtained.
It should be noted that, a failure involved by the deformation of the above-described seat is a case where the bosses fail to be in contact with one another when the valve disc is used for the damper and when the valve discs are vertically stacked and are handled regardless of the seat shape, whether to install the piston rings, and the mounting method. This failure possibly occurs when the outer diameters (distances from the valve discs to the outer peripheral ends of the respective seats) of the seats on both sides differ.
An object of the present invention is to provide a valve where bosses are not in contact with one another when the valve discs are vertically stacked and handled, and even if outer diameters of seats on both sides differ, a deformation of the seats can be restrained.
According to one aspect of the present invention, a valve includes: a valve disc that partitions one chamber and another chamber; and annular-plate shaped leaf valves laminated on each of the one chamber side and the other chamber side of the valve disc, wherein the valve disc includes: an annular boss formed at each of the one chamber side and the other chamber side to support the leaf valves; a seat formed on an outer peripheral side of the boss on each of the one chamber side and the other chamber side, the leaf valves being left from/seated on the seats; an opening surrounded by each of the seats; one passage that allows the one chamber to communicate with the opening at the other chamber side; and another passage that allows the other chamber to communicate with the opening at the one chamber side, at least one of the seats on the one chamber side and the other chamber side is disposed to project with respect to the bosses, an outer peripheral end of the seat on the one chamber side is disposed on an outer peripheral side with respect to an outer peripheral end of the seat on the other chamber side, and the valve disc includes an auxiliary seat formed on an outer peripheral side of the seat on the other chamber side, the auxiliary seat being disposed at a height identical to the seat on the other chamber side, alternatively, the auxiliary seat projecting with respect to the seat on the other chamber side.